<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>value属性值</title>
    <script type="text/javascript" src="../js/jquery-3.4.1.min.js"></script>
    <script>
        $(function(){
           $("#username").blur(function(){
              console.log("用户名:"+$(this).attr("value"));
              console.log("用户名:"+$(this).prop("value"));
              console.log("用户名:"+$(this).val());
               $(this).prop("value","123456")
               $(this).val("jack")
           });
        });
    </script>
</head>
<body>
用户名:<input type="text" id="username">
</body>
</html>